This Waltham "three bearing slide spindle" Nashua 3 lathe has a spring collet for holding wire rods that are released by a foot-activated sliding spindle. The collet is stationary and the spindle moves back away to open the collet. The three bearing sliding spindle was invented in the Waltham factory in the 1850's probably by Charles S. Moseley. It eliminated the problem of varying length or thickness of parts due to variable tension on the collet draw bar or slight differences in the stock diameter. This form of construction, although modified in some particulars, was almost universally adopted by all watch factories and builders of automatic production machiners and is still in use today. Notice the cam activated slide spindle on Charles Vander Woerd's automatic screw machine.
On the lathe bed is a double slide rest with one tool for turning down the wire to form the body of the screw and another tool for cutting it off. The lathes is also provided with a swing or tumble tail stock containing two or more spindles, one of which serves as a stop to control the length of the screw and another that carries the threading die. The careful hand of the operator was necessary to avoid twisting off the screw in the die came into contact with the underside of the head during the threading process.
After the threading operation, the cutting off tool was brought into action and the wire rod partially severed, leaving enough metal to support the screw. At this point the operator would pick up a "slotting plate" that had even rows of tapped holes, hold it up to the nearly severed screw and run the screw into a tapped hole until the head came into contact with the plate and parted with the rod by twisting off. When the slotting plate was full, it was placed in a slotting machine where each row of screws was slotted. The screws were then removed by a boy who returned the plate to the lathe operator for another filling. A skilled operator could make about 1,500 screws a day by this method.